mains powered drill for a very big hole saw (7 inch)

[blackrose]

How are you holding onto a drill with a 7" dia hole cutter? I once tried to cut a 4" diameter hole into my steel roof and the torque was so great it almost ripped the drill out of my hands even with a side handle. I gave up and used a jigsaw in the end.

[Neil Smith]

I cut a 6" hole for the flue collar with a hole saw in an 18v dewalt but slowly with lots of cutting oil and rested drill every 5 mins to cool down. I have also got a huge wolf with 3/4" chuck you could borrow but is very heavy and if it snagged it would swing you around so no claims please you have been warned.

 

Neil

[Guest User]

How about a 5kg SDS+ drill used on the 'drill only' setting - Screwfix do one for £60 - a fairly cheap way to get a robust 1800watt mains drill? http://m.screwfix.com/p/titan-ttb278sds-5kg-sds-drill-230-240v/97533

 

LCx

[craftycarper]

How are you holding onto a drill with a 7" dia hole cutter? I once tried to cut a 4" diameter hole into my steel roof and the torque was so great it almost ripped the drill out of my hands even with a side handle. I gave up and used a jigsaw in the end.

the hilti that I have is just for hole cutting only and has a very good clutch that stops it taking your arm off

[magnetman]

How are you holding onto a drill with a 7" dia hole cutter? I once tried to cut a 4" diameter hole into my steel roof and the torque was so great it almost ripped the drill out of my hands even with a side handle. I gave up and used a jigsaw in the end.

Take it easy and don't push too hard. Plenty of cutting compound makes it smoother. Both hands on the drill one holding the bottom of the battery to stabilise it.

 

An advantage of the makita 14.4v drill (6337D) I used is it will stall before bending my wrist damage to drill is better than damage to me.

 

It does still work OK so perhaps I should stick with that - as mentioned previously a bit at a time then rest the drill.

 

I think the best thing may be to start cutting it with the holesaw to get a groove into the steel then use that groove to guide the jigsaw round. I can cut steel with the jigsaw no problem but do have trouble getting a very accurate circle..

It's an old Wolf, so not available now!

I could get it to Chessington on Saturday if that's any good to you.

 

Richard

Thanks for the offer but I think I will tackle it with what i have and I think those heavy duty things may be a bit dangerous

[TheBiscuits]

I think the best thing may be to start cutting it with the holesaw to get a groove into the steel then use that groove to guide the jigsaw round. I can cut steel with the jigsaw no problem but do have trouble getting a very accurate circle..

That sounds like a good plan. Could you also use a wooden template (smaller circle) to follow with the jigsaw?

[magnetman]

That's a good idea cut a plywood disc with the holesaw and bolt it to the hull side then use it as a guide.

 

Thanks for that

Perhaps I could even bolt the jigsaw to the wooden disc and rotate it around like a compass !

[ChimneyChain]

Drill the series of holes thing Jigsaw out then use a 5" angle grinder with a grinding disc on and keep going around the inside of the hole until lovely and smooth.

 

Darren

[Batavia]

Perhaps I could even bolt the jigsaw to the wooden disc and rotate it around like a compass !

This actually works quite well, but just fit a trammel bar to the jigsaw's sole plate, which can then be attached to a bolt through the hole's centre. Many years ago, some Bosch jigsaws were supplied with such an attachment, but I haven't seen a proprietary one for a long while. Easy to knock up something suitable, and you get a pretty perfect circle.

 

 

Chris G

[David Mack]

This actually works quite well, but just fit a trammel bar to the jigsaw's sole plate, which can then be attached to a bolt through the hole's centre. Many years ago, some Bosch jigsaws were supplied with such an attachment, but I haven't seen a proprietary one for a long while. Easy to knock up something suitable, and you get a pretty perfect circle.

 

 

Chris G

 

The ancient B&D jigsaw I used to have came with a side fence attachment. At the opposite end to the fence part there was a 3-4mm hole through. By turning the fence upside down, you could put a bolt through the this hole and a hole drilled in the centre of the work, and use it as a trammel as Chris G suggests.

 

I never did it with the jigsaw, but I have done something similar with a router to finish the semi-circular top of an arched wooden window frame. It worked just fine.

[magnetman]

I will have a go making such a thing for my makita jigsaw

[TheBiscuits]

I will have a go making such a thing for my makita jigsaw

Photos please.

 

That sounds like the best idea yet.

[the barnacle]

think i would just burn a few second hand drills out, pop to the car boot for them.

[Batavia]

I will have a go making such a thing for my makita jigsaw

Just to add a cautionary note - I have found that this works well for thin-ish materials (your steel should be fine) but if you try it on thick (2") stuff, the bottom of the cut can bear little relationship to the top.

 

If you still have to do your wooden bits, I would suggest either a hole saw used in a pillar drill or a router with a deep cutter, again using a trammel bar.

 

Chris G

Edited September 9, 2015 by Batavia

[magnetman]

Thanks

I will do the wood with the holesaw as I have done 2 like that and achieved a very nice finish